Mobile storage devices with flash memory mediums have been widely used and have gradually replaced the floppy disk. However, shortcomings of the flash memory medium also exist in applications. For example, when writing new data into a flash memory medium or modifying the saved data, people need firstly to “transfer” the data of a memory block specified by the respective physical address to another memory block specified by another address because of the well-known specific read-write characteristics of the flash memory medium.
The principle of data reading by the flash memory medium resembles that by a hard disk of PC, both acquire information in the disk by reading a file allocation table, directory and the like. If a false power cut occurs by accident or the misoperation of a user during the process of transferring the original data, the process will be interrupted. Thus the transfer of the original data is not finished when the false power cut occurs, and the part of the original data is not updated in the file allocation table, directory and the like. Finally, the data involved in the transfer will be unreadable and become invalid data. Therefore, files containing the part of data that have been saved become invalid and a data loss is thus caused.
Additionally, because of the specific read-write characteristics of the flash memory medium, an erasure operation for the memory block is needed, which requires all bits in the memory block are set with logic value “1”. If a false power cut occurs during the erasure operation, there may be a condition that some bits in the memory block may have been set with logic value “1”, while the remaining bits may still be in logic value “0”, and errors will occur when new data is written into said memory block.